An IfcObject is the generalization of any semantically treated thing or process. Objects are things as they appear - i.e. occurrences.

NOTE  Examples of IfcObject include physically tangible items such as wall, beam or covering, physically existing items such as spaces, or conceptual items such as grids or virtual boundaries. It also stands for processes such as work tasks, for controls such as cost items, or for actors such as persons involved in the design process.

Objects can be named, using the inherited Name attribute, which should be a user recognizable label for the object occurrance. Further explanations to the object can be given using the inherited Description attribute. The ObjectType attribute is used:

• to store the user defined value for all subtypes of IfcObject, where a PredefinedType attribute is given, and its value is set to USERDEFINED.
• to provide a type information (could be seen as a very lightweight classifier) of the subtype of IfcObject, if no PredefinedType attribute is given. This is often the case, if no comprehensive list of predefined types is available.

Objects are independent pieces of information that might contain or reference other pieces of information. There are several relationships in which objects can be involved:

• Association to external/internal resource information - an association relationship that refers to external/internal sources of information. See supertype IfcObjectDefinition for more information.
• Assignment of other objects - an assignment relationship that refers to other types of objects. See supertype IfcObjectDefinition for more information.
• Aggregation of other objects - an aggregation relationship that establishes a whole/part relation. Objects can either be a whole, or a part, or both. See supertype IfcObjectDefinition for more information.
• Assignment of a type : IsTypedBy - a definition relationship IfcRelDefinesByType that uses a type definition to define the common characteristics of this occurrences, potentially including the common shape representation and common properties of all object occurrences assigned to this type. It is a specific - occurrence relationship with implied dependencies (as the occurrence properties depend on the properties of the type, but may override them).
• Assignment of a partial type : IsDeclaredBy, Declares - a definition relationship IfcRelDefinesByObject that uses a component of a type definition (a part of a type, called the "declaring part") to define a component of an occurence (part of occurrence, called the "reflected part"). This is also refered to as a "deep copy". The common characteristics of all parts in the occurrence are defined by parts in the type. It is a specific - occurrence relationship with implied dependencies (as the occurrence properties depend on the properties of the type, but may override them).
• Assignment of property sets : IsDefinedBy - a definition relationship IfcRelDefinesByProperties that assignes property set definitions to the object occurrence.

NOTE  See IfcRelDefinesByType for an explanatory figure. Also see there for how to override type properties by occurrence properties. See IfcRelDefinesByObject for an explanatory figure for the assignment of a partial type.

HISTORY  New entity in IFC1.0

IFC4 CHANGE  The inverse relationships Declares, IsDeclaredBy, and IsTypedBy have been added, types are not longer included in the IsDefinesBy relationship. IfcProject has been promoted to be a subtype of IfcObjectDefinition -> IfcContext.

Informal Propositions:

1. A partial type assignment, i.e. the inverse attribute IsDeclaredBy, or Declares shall only be used, if the object is part of a decomposition, i.e. if either IsDecomposedBy, or Decomposes is exerted.

The Object User Identity concept applies to this entity.

An attribute Name and optionally Description can be used for all subypes of IfcObject. For those subtypes, that have an object type definition, such as ifcBeam - IfcBeamType, the common Name and optionally Description is associated with the object type.

The Object Predefined Type concept applies to this entity.

The Object Typing concept applies to this entity.

Any object occurrence can be typed by being assigned to a common object type utilizing this concept. A particular rule, restricting the applicable subtypes of IfcTypeObject that can be assigned, is introduced by overriding this concept at the level of subtypes of IfcObject.

The Property Sets for Objects concept applies to this entity.

Any object occurrence can hold property sets, each being a set of individual properties having name, description, value(s) and unit(s). A reference to applicable property sets, being part of this specification, is introduced at the level of sub types of IfcObject.

The Property Sets with Override concept applies to this entity.

Any object occurrence can hold property sets, either directly at the object occurrence as element specific property sets, or at the object type, as type property sets. In this case, the properties that are provided to the object occurrence are the combinations of element specific and type properties. In case, that the same property (within the same property set, is defined both, in occurrence and type properties, the property value of the occurrence property overrides the property value of the type property.